LIBERAL Democrats at a UK level must not repeat the mistakes made by Plaid Cymru as a junior partner in a coalition, Welsh leader Kirsty Williams warned last night.

The Brecon & Radnorshire AM will address the UK conference, which starts today, on Wednesday and she is adamant that the party must reach out beyond its core voters to show the British public that it is a force for good in government.

Ms Williams does not want to see Lib Dems slip backwards at the next election and repeat the experience of Plaid. Ieuan Wyn Jones’ party shared power with Labour in the Assembly but was pushed into third place behind the Conservatives in the May elections. Arguing that there are important lessons to be learned, she said that during the election campaign Plaid trumpeted its achievements on devolution and the Welsh language but sent “mixed messages” about health, education and the economy.

She said: “Those mixed messages Plaid gave out were one of the reasons they couldn’t capitalise on being part of that government. What was it about Plaid being in government that had made that government different?”

She continued: “What that should tell Liberal Democrats is that if you are in government, like we are in Westminster, we need to be absolutely clear that whilst we work on issues that are hugely important to Liberal Democrats’ core voters it’s also being sure we can demonstrate to the British public at large that Liberal Democrats are making a difference on the bread and butter issues of the day and standing up and being and very clear and communicating what is the difference the Liberal Democrats in government are making.”

Arguing that the Lib Dems must stop thinking like an opposition party, she said: “I think psychologically if you’ve been a party of opposition for many, many, many years it can be a bit of a mind-change but it has to be done.

“There are very good reasons why the Liberal Democrats are in the Government in Westminster, there are very good examples of the difference that Liberal Democrat presence is making and we need to stand up and proud about that.”

In the Assembly, Ms Williams said, Lib Dems will not try and wreck First Minister Carwyn Jones’ budget if he brings forward plans for health and education which they can support.

She said: “We won’t pull any punches where we feel the Labour party are going wrong but nor will we create tensions where there is no need for them to exist.”

Stating that Wales needs “stable government,” she said: “Carwyn said himself his party hasn’t a monopoly on good ideas.

“He has to work with others and we are ready to play that constructive role if we feel the Labour party is serious about tackling educational outcomes, tackling the health service [and] making sure we’ve got good value for the budget that we’ve got.”

Ms Williams is not fighting the reduction in the number of Westminster constituencies from 40 to 30 in Wales which Shadow Welsh Secretary Peter Hain has said would result in a “massacre” of community links; full proposals will be published in the new year.

She said: “[Given] we’ve got the new powers from the referendum I think it’s an appropriate time to look at the levels of representation.”

Ms Williams described 2011 as “one of the most exhilarating years in Welsh politics” while acknowledging there have been “highs and lows”.

The Welsh party slipped from six to five members but avoided “the wipe-out that everybody predicted”. There was further drama when newly elected AM John Dixon was disqualified because of his membership of the Care Council for Wales.

But with his replacement installed and the party staking out its territory in a strengthened Assembly Ms Williams strikes an upbeat tone. She insists there is a “job to be done”.